669684 - Avoid allocating a chunk for time-based GC trigger

Status: NEW

(Core :: JavaScript Engine, defect)

Description

[Gregor Wagner [:gwagner]]

Right now we have to allocate a chunk in order to trigger the new time based GC. We could also trigger it when the last chunk with free arenas is picked and avoid a heap-growth. Should be another fragmentation improvement.

Comment 1

[Nicholas Nethercote [inactive]]

IIUC, the net effect is that we will avoid allocating a new chunk (and putting a single object into it just before doing GC) every time a time-based GC occurs.  Is that right?  Sounds like a small win, but a good one.

Comment 2

[Gregor Wagner [:gwagner]]

(In reply to comment #1)
> IIUC, the net effect is that we will avoid allocating a new chunk (and
> putting a single object into it just before doing GC) every time a
> time-based GC occurs.  Is that right?  Sounds like a small win, but a good
> one.

We perform the GC when we return from executing a script so it's not like we allocate a chunk, put a single object in there and perform a GC right away.

But yes we can avoid allocating the new chunk in the low-allocation-rate situations.